Cilia-of-Gold

A.D. 3948

The peoplethough exhausted by the tunnel’s coldhad rested long enough, Cilia-of-Gold decided.

Now it was time to fight.

She climbed up through the water, her flukes pulsing, and prepared to lead the group further along the Ice-tunnel to the new Chimney cavern.

But, even as the people rose from their browsing and crowded through the cold, stale water behind her, Cilia-of-Gold’s resolve wavered. The Seeker was a heavy presence inside her. She could feel its tendrils wrapped around her stomach, andshe knewits probes must already have penetrated her brain, her mind, her self.

With a beat of her flukes, she thrust her body along the tunnel. She couldn’t afford to show weakness. Not now.

“Cilia-of-Gold.”

A broad body, warm through the turbulent water, came pushing out of the crowd to bump against hers: it was Strong-Flukes, one of Cilia-of-Gold’s Three-mates. Strong-Flukes’ presence was immediately comforting. “Cilia-of-Gold. I know something’s wrong.”

Cilia-of-Gold thought of denying it; but she turned away, her depression deepening. “I couldn’t expect to keep secrets from you. Do you think the others are aware?”

The hairlike cilia lining Strong-Flukes’ belly barely vibrated as she spoke. “Only Ice-Born suspects something is wrong. And if she didn’t, we’d have to tell her.” Ice-Born was the third of Cilia-of-Gold’s mates.

“I can’t afford to be weak, Strong-Flukes. Not now.”

As they swam together, Strong-Flukes flipped onto her back. Tunnel water filtered between Strong-Flukes’ carapace and her body; her cilia flickered as they plucked particles of food from the stream and popped them into the multiple mouths along her belly. “Cilia-of-Gold,” she said. “I know what’s wrong. You’re carrying a Seeker, aren’t you?”

“…Yes. How could you tell?”

“I love you,” Strong-Flukes said. “That’s how I could tell.”

The pain of Strong-Flukes’ perception was as sharp, and unexpected, as the moment when Cilia-of-Gold had first detected the signs of the infestation in herself… and had realized, with horror, that her life must inevitably end in madness, in a purposeless scrabble into the Ice over the world. “It’s still in its early stages, I think. It’s like a huge heat, inside me. And I can feel it reaching into my mind. Oh, Strong-Flukes…”

“Fight it.”

“I can’t. I”

“You can. You must.”

The end of the tunnel was an encroaching disc of darkness; already Cilia-of-Gold could feel the inviting warmth of the Chimney-heated water on the cavern beyond.

This should have been the climax, the supreme moment of Cilia-of-Gold’s life.

The group’s old Chimney, with its fount of warm, rich water, was failing; and so they had to flee, and fight for a place in a new cavern.

That, or die.

It was Cilia-of-Gold who had found the new Chimney, as she had explored the endless network of tunnels between the Chimney caverns. Thus, it was she who must lead this warSeeker or no Seeker.

She gathered up the fragments of her melting courage.

“You’re the best of us, Cilia-of-Gold,” Strong-Flukes said, slowing. “Don’t ever forget that.”

Cilia-of-Gold pressed her carapace against Strong-Flukes’ in silent gratitude.

Cilia-of-Gold turned and clacked her mandibles, signaling the rest of the people to halt. They did so, the adults sweeping the smaller children inside their strong carapaces.

Strong-Flukes lay flat against the floor and pushed a single eye stalk towards the mouth of the tunnel. Her caution was wise; there were species who could home in on even a single sound-pulse from an unwary eye.

After some moments of silent inspection, Strong-Flukes wriggled back along the Ice surface to Cilia-of-Gold.

She hesitated. “We’ve got problems, I think,” she said at last.

The Seeker seemed to pulse inside Cilia-of-Gold, tightening around her gut. “What problems?”

“This Chimney’s inhabited already. By Heads.”

Kevan Scholes stopped the rover a hundred yards short of the wall-mountain’s crest.

Irina Larionova, wrapped in a borrowed environment suit, could tell from the tilt of the cabin that the surface here was inclined upwards at around forty degreesshallower than a flight of stairs. This “mountain,” heavily eroded, was really little more than a dust-clad hill, she thought.

“The wall of Chao Meng-Fu Crater,” Scholes said briskly, his radio-distorted voice tinny. “Come on. We’ll walk to the summit from here.”

“Walk?” She studied him, irritated. “Scholes, I’ve had one hour’s sleep in the last thirty-six; I’ve traveled across ninety million miles to get here, via flitters and wormhole transit linksand you’re telling me I have to walk up this damn hill?”

Scholes grinned through his face plate. He was AS-preserved at around physical-twenty-five, Larionova guessed, and he had a boyishness that grated on her. Damn it, she reminded herself, this “boy” is probably older than me.

“Trust me,” he said. “You’ll love the view. And we have to change transports anyway.”

“Why?”

“You’ll see.”

He twisted gracefully to his feet. He reached out a gloved hand to help Larionova pull herself, awkwardly, out of her seat. When she stood on the cabin’s tilted deck, her heavy boots hurt her ankles.

Scholes threw open the rover’s lock. Residual air puffed out of the cabin, crystallizing. The glow from the cabin interior was dazzling; beyond the lock, Larionova saw only darkness.

Scholes climbed out of the lock and down to the planet’s invisible surface. Larionova followed him awkwardly; it seemed a long way to the lock’s single step.

Her boots settled to the surface, crunching softly. The lock was situated between the rover’s rear wheels: the wheels were constructs of metal strips and webbing, wide and light, each wheel taller than she was.

Scholes pushed the lock closed, and Larionova was plunged into sudden darkness.

Scholes loomed before her. He was a shape cut out of blackness. “Are you okay? Your pulse is rapid.”

She could hear the rattle of her own breath, loud and immediate. “Just a little disoriented.”

“We’ve got all of a third of a gee down here, you know. You’ll get used to it. Let your eyes dark-adapt. We don’t have to hurry this.”

She looked up.

In her peripheral vision, the stars were already coming out. She looked for a bright double star, blue and white. There it was: Earth, with Luna.

And now, with a slow grandeur, the landscape revealed itself to her adjusting eyes. The plain from which the rover had climbed spread out from the foot of the crater wall-mountain. It was a complex patchwork of crowding craters, ridges and scarpssome of which must have been miles highall revealed as a glimmering tracery in the starlight. The face of the planet seemed wrinkled, she thought, as if shrunk with age.

“These wall-mountains are over a mile high,” Scholes said. “Up here, the surface is firm enough to walk on; the regolith dust layer is only a couple of inches thick. But down on the plain the dust can be ten or fifteen yards deep. Hence the big wheels on the rover. I guess that’s what five billion years of thousand-degree temperature range does for a landscape…”

Just twenty-four hours ago, she reflected, Larionova had been stuck in a boardroom in New York, buried in one of Superet’s endless funding battles. And now this… wormhole travel was bewildering. “Lethe’s waters,” she said. “It’s sodesolate.”

Scholes gave an ironic bow. “Welcome to Mercury,” he said.

Cilia-of-Gold and Strong-Flukes peered down into the Chimney cavern.

Cilia-of-Gold had chosen the cavern well. The Chimney here was a fine young vent, a glowing crater much wider than their old, dying home. The water above the Chimney was turbulent, and richly cloudy; the cavern itself was wide and smooth-walled. Cilia-plants grew in mats around the Chimney’s base. Cutters browsed in turn on the cilia-plants, great chains of them, their tough little arms slicing steadily through the plants. Sliding through the plant mats Cilia-of-Gold could make out the supple form of a Crawler, its mindless, tubelike body wider than Cilia-of-Gold’s and more than three times as long…

And, stalking around their little forest, here came the Heads themselves, the rulers of the cavern. Cilia-of-Gold counted four, five, six of the Heads, and no doubt there were many more in the dark recesses of the cavern.

One Headclose to the tunnel mouthswiveled its huge, swollen helmet-skull towards her.

She ducked back into the tunnel, aware that all her cilia were quivering.

Strong-Flukes drifted to the tunnel floor, landing in a little cloud of food particles. “Heads,” she said, her voice soft with despair. “We can’t fight Heads.”

The Heads’ huge helmet-skulls were sensitive to heatfantastically so, enabling the Heads to track and kill with almost perfect accuracy. Heads were deadly opponents, Cilia-of-Gold reflected. But the people had nowhere else to go.

“We’ve come a long way, to reach this place, Strong-Flukes. If we had to undergo another journey” through more cold, stagnant tunnels “many of us couldn’t survive. And those who did would be too weakened to fight.

“No. We have to stay hereto fight here.”

Strong-Flukes groaned, wrapping her carapace close around her. “Then we’ll all be killed.”

Cilia-of-Gold tried to ignore the heavy presence of the Seeker within herand its prompting, growing more insistent now, that she get away from all this, from the crowding presence of peopleand she forced herself to think.

Larionova followed Kevan Scholes up the slope of the wall-mountain. Silicate surface dust compressed under her boots, like fine sand. The climbing was easyit was no more than a steep walk, reallybut she stumbled frequently, clumsy in this reduced gee.

They reached the crest of the mountain. It wasn’t a sharp summit: more a wide, smooth platform, fractured to dust by Mercury’s wild temperature range.

“Chao Meng-Fu Crater,” Scholes said. “A hundred miles wide, stretching right across Mercury’s South Pole.”

The crater was so large that even from this height its full breadth was hidden by the tight curve of the planet. The wall-mountain was one of a series that swept across the landscape from left to right, like a row of eroded teeth, separated by broad, rubble-strewn valleys. On the far side of the summit, the flanks of the wall-mountain swept down to the plain of the crater, a full mile below.

Mercury’s angry Sun was hidden beyond the curve of the world, but its corona extended delicate, structured tendrils above the far horizon.

The plain itself was immersed in darkness. But by the milky, diffuse light of the corona, Larionova could see a peak at the center of the plain, shouldering its way above the horizon. There was a spark of light at the base of the central peak, incongruously bright in the crater’s shadows: that must be the Thoth team’s camp.

“This reminds me of the Moon,” she said.

Scholes considered this. “Forgive me, Dr. Larionova. Have you been down to Mercury before?”

“No,” she said, his easy, informed arrogance grating on her. “I’m here to oversee the construction of Thoth, not to sightsee.”

“Well, there’s obviously a superficial similarity. After the formation of the main System objects five billion years ago, all the inner planets suffered bombardment by residual planetesimals. That’s when Mercury took its biggest strike: the one which created the Caloris feature. But after that, Mercury was massive enough to retain a molten coreunlike the Moon. Later planetesimal strikes punched holes in the crust, so there were lava outflows that drowned some of the older cratering.

“Thus, on Mercury, you have a mixture of terrains. There’s the most ancient landscape, heavily cratered, and the planitia: smooth lava plains, punctured by small, young craters.

“Later, as the core cooled, the surface actually shrunk inwards. The planet lost a mile or so of radius.”

Like a dried-out tomato. “So the surface is wrinkled.”

“Yes. There are rupes and dorsa: ridges and lobate scarps, cliffs a couple of miles tall and extending for hundreds of miles. Great climbing country. And in some places there are gas vents, chimneys of residual thermal activity.” He turned to her, corona light misty in his face plate. “So Mercury isn’t really so much like the Moon at all… Look. You can see Thoth.”

She looked up, following his pointing arm. There, just above the far horizon, was a small blue star.

She had her face plate magnify the image. The star exploded into a compact sculpture of electric blue threads, surrounded by firefly lights: the Thoth construction site.

Thoth was a habitat to be placed in orbit close to Sol. Irina Larionova was the consulting engineer contracted by Superet to oversee the construction of the habitat.

At Thoth, a Solar-interior probe would be constructed. The probe would be one Interface of a wormhole, loaded with sensors. The Interface would be dropped into the Sun. The other Interface would remain in orbit, at the center of the habitat.

Thoth’s purpose was to find out what was wrong with the Sun.

Irina Larionova wasn’t much interested in the purpose of Thoth, or any of Superet’s semi-mystical philosophizing. It was the work that was important, for her: and the engineering problems posed by Thoth were fascinating.

The electric-blue bars she could see now were struts of exotic matter, which would eventually frame the wormhole termini. The sparks of light moving around the struts were GUTships and short-haul flitters. She stared at the image, wishing she could get back to some real work.

Irina Larionova had had no intention of visiting Mercury herself. Mercury was a detail, for Thoth. Why would anyone come to Mercury, unless they had to? Mercury was a piece of junk, a desolate ball of iron and rock too close to the Sun to be interesting, or remotely habitable. The two Thoth exploratory teams had come here only to exploit: to see if it was possible to dig raw materials out of Mercury’s shallowand close-at-handgravity well, for use in the construction of the habitat. The teams had landed at the South Pole, where traces of water-ice had been detected, and at the Caloris Basin, the huge equatorial crater whereit was hopedthat ancient impact might have brought iron-rich compounds to the surface.

The flitters from Thoth actually comprised the largest expedition ever to land on Mercury.

But, within days of landing, both investigative teams had reported anomalies.

Larionova tapped at her suit’s sleeve-controls. After a couple of minutes an image of Dolores Wu appeared in one corner of Larionova’s face plate. Hi, Irina, she said, her voice buzzing like an insect in Larionova’s helmet’s enclosed space.

Dolores Wu was the leader of the Thoth exploratory team in Caloris. Wu was Mars-born, with small features and hair grayed despite AntiSenescence treatments. She looked weary.

“How’s Caloris?” Larionova asked.

Well, we don’t have much to report yet. We decided to start with a detailed gravimetric survey…

“And?”

We found the impact object. We think. It’s as massive as we thought, but muchmuchtoo small, Irina. It’s barely a mile across, way too dense to be a planetesimal fragment.

“A black hole?”

No. Not dense enough for that.

“Then what?”

Wu looked exasperated. We don’t know yet, Irina. We don’t have any answers. I’ll keep you informed.

Wu closed off the link.

Standing on the corona-lit wall of Chao Meng-Fu Crater, Larionova asked Kevan Scholes about Caloris.

“Caloris is big,” he said. “Luna has no impact feature on the scale of Caloris. And Luna has nothing like the Weird Country in the other hemisphere…”

“The what?”

A huge planetesimalor somethinghad struck the equator of Mercury, five billion years ago, Scholes said. The Caloris Basinan immense, ridged crater systemformed around the primary impact site. Whatever caused the impact was still buried in the planet, somewhere under the crust, dense and massive; the object was a gravitational anomaly which had helped lock Mercury’s rotation into synchronization with its orbit.

“Away from Caloris itself, shock waves spread around the planet’s young crust,” Scholes said. “The waves focused at Caloris’ antipodethe point on the equator diametrically opposite Caloris itself. And the land there was shattered, into a jumble of bizarre hill and valley formations. The Weird Country… hey. Dr. Larionova.”

She could hear that damnable grin of Scholes’s. “What now?” she snapped.

He walked across the summit towards her. “Look up,” he said.

“Damn it, Scholes”

There was a pattering against her face plate.

She tilted up her head. Needle-shaped particles swirled over the wall-mountain from the planet’s dark side and bounced off her face plate, sparkling in corona light.

“What in Lethe is that?”

“Snow,” he said.

Snow… on Mercury?

In the cool darkness of the tunnel, the people clambered over each other; they bumped against the Ice walls, and their muttering filled the water with criss-crossing voice-ripples. Cilia-of-Gold swam through and around the crowd, coaxing the people to follow her will.

She felt immensely weary. Her concentration and resolve threatened continually to shatter under the Seeker’s assault. And the end of the tunnel, with the deadly Heads beyond, was a looming, threatening mouth, utterly intimidating.

At last the group was ready. She surveyed them. All of the peopleexcept the very oldest and the very youngestwere arranged in an array which filled the tunnel from wall to wall; she could hear flukes and carapaces scraping softly against Ice.

The people looked weak, foolish, eager, she thought with dismay; now that she was actually implementing it her scheme seemed simple-minded. Was she about to lead them all to their deaths?

But it was too late for the luxury of doubt, she told herself. Now, there was no other option to follow.

She lifted herself to the axis of the tunnel, and clacked her mandibles sharply.

“Now,” she said, “it is time. The most important moment of your lives. And you must swim! Swim as hard as you can; swim for your lives!”

And the people responded.

There was a surge of movement, of almost exhilarating intent. The people beat their flukes as one, and a jostling mass of flesh and carapaces scrapped down the tunnel.

Cilia-of-Gold hurried ahead of them, leading the way towards the tunnel mouth. As she swam she could feel the current the people were creating, the plug of cold tunnel water they pushed ahead of themselves.

Within moments the tunnel mouth was upon her.

She burst from the tunnel, shooting out into the open water of the cavern, her carapace clenched firm around her. She was plunged immediately into a clammy heat, so great was the temperature difference between tunnel and cavern.

Above her the Ice of the cavern roof arched over the warm chimney mouth. And from all around the cavern, the helmet skulls of Heads snapped around towards her.

Now the people erupted out of the tunnel, a shield of flesh and chitin behind her. The rush of tunnel water they pushed ahead of themselves washed over Cilia-of-Gold, chilling her new.

She tried to imagine this from the Heads’ point of view. This explosion of cold water into the cavern would bring about a much greater temperature difference than the Heads’ heat-sensor skulls were accustomed to; the Heads would be dazzled, at least for a time: long enoughshe hopedto give her people a fighting chance against the more powerful Heads.

She swiveled in the water. She screamed at her people, so loud she could feel her cilia strain at the turbulent water. “Now! Hit them now!”

The people, with a roar, descended towards the Heads.

Kevan Scholes led Larionova down the wall-mountain slope into Chao Meng-Fu Crater.

After a hundred yards they came to another rover. This car was similar to the one they’d abandoned on the other side of the summit, but it had an additional fitting, obviously improvised: two wide, flat rails of metal, suspended between the wheels on hydraulic legs.

Scholes helped Larionova into the rover and pressurized it. Larionova removed her helmet with relief. The rover smelled, oppressively, of metal and plastic.

While Scholes settled behind his controls, Larionova checked the rover’s data desk. An update from Dolores Wu was waiting for her. Wu wanted Larionova to come to Caloris, to see for herself what had been found there. Larionova sent a sharp message back, ordering Wu to summarize her findings and transmit them to the data desks at the Chao site.

Wu acknowledged immediately, but replied: I’m going to find this hard to summarize, Irina.

Larionova tapped out: Why?

We think we’ve found an artifact.

Larionova stared at the blunt words on the screen.

She massaged the bridge of her nose; she felt an ache spreading out from her temples and around her eye sockets. She wished she had time to sleep.

Scholes started the vehicle up. The rover bounced down the slope, descending into shadow. “It’s genuine water-ice snow,” Scholes said as he drove. “You know that a day on Mercury lasts a hundred and seventy-six Earth days. It’s a combination of the eighty-eight-day year and the tidally locked rotation, which”

“I know.”

“During the day, the Sun drives water vapor out of the rocks and into the atmosphere.”

“What atmosphere?”

“You really don’t know much about Mercury, do you? It’s mostly helium and hydrogenonly a billionth of Earth’s sea-level pressure.”

“How come those gases don’t escape from the gravity well?”

“They do,” Scholes said. “But the atmosphere is replenished by the Solar wind. Particles from the Sun are trapped by Mercury’s magnetosphere. Mercury has quite a respectable magnetic field: the planet has a solid iron core, which…”

She let Scholes’ words run on through her head, unregistered. Air from the Solar wind, and snow at the South Pole…

Maybe Mercury was a more interesting place than she’d imagined.

“Anyway,” Scholes was saying, “the water vapor disperses across the planet’s sunlit hemisphere. But at the South Pole we have this crater: Chao Meng-Fu, straddling the Pole itself. Mercury has no axial tiltthere are no seasons hereand so Chao’s floor is in permanent shadow.”

“And snow falls.”

“And snow falls.”

Scholes stopped the rover and tapped telltales on his control panel. There was a whir of hydraulics, and she heard a soft crunch, transmitted into the cabin through the rover’s structure.

Then the rover lifted upwards through a foot.

The rover lurched forward again. The motion was much smoother than before, and there was an easy, hissing sound.

“You’ve just lowered those rails,” Larionova said. “I knew it. This damn rover is a sled, isn’t it?”

“It was easy enough to improvise,” Scholes said, sounding smug. “Just a couple of metal rails on hydraulics, and vernier rockets from a cannibalized flitter to give us some push…”

“It’s astonishing that there’s enough ice here to sustain this.”

“Well, that snow may have seemed sparse, but it’s been falling steadilyfor five billion years… Dr. Larionova, there’s a whole frozen ocean here, in Chao Meng-Fu Crater: enough ice to be detectable even from Earth.”

Larionova twisted to look out through a viewport at the back of the cabin. The rover’s rear lights picked out twin sled tracks, leading back to the summit of the wall-mountain; ice, exposed in the tracks, gleamed brightly in starlight.

Lethe, she thought. Now I’m skiing. Skiing, on Mercury. What a day.

The wall-mountain shallowed out, merging seamlessly with the crater plain. Scholes retracted the sled rails; on the flat, the regolith dust gave the ice sufficient traction for the rover’s wide wheels. The rover made fast progress through the fifty miles to the heart of the plain.

Larionova drank coffee and watched the landscape through the view ports. The corona light was silvery and quite bright here, like Moonlight. The central peak loomed up over the horizon, like some approaching ship on a sea of dust. The ice surface of Chao’s floorthough packed with craters and covered with the ubiquitous regolith dustwas visibly smoother and more level than the plain outside the crater.

The rover drew to a halt on the outskirts of the Thoth team’s sprawling camp, close to the foothills of the central peak. The dust here was churned up by rover tracks and flitter exhaust splashes, and semitransparent bubble-shelters were hemispheres of yellow, homely light, illuminating the darkened ice surface. There were drilling rigs, and several large pits dug into the ice.

Scholes helped Larionova out onto the surface. “I’ll take you to a shelter,” he said. “Or a flitter. Maybe you want to freshen up before”

“Where’s Dixon?”

Scholes pointed to one of the rigs. “When I left, over there.”

“Then that’s where we’re going. Come on.”

Frank Dixon was the team leader. He met Larionova on the surface, and invited her into a small opaqued bubble-shelter nestling at the foot of the rig.

Scholes wandered off into the camp, in search of food.

The shelter contained a couple of chairs, a data desk, and a basic toilet. Dixon was a morose, burly American; when he took off his helmet there was a band of dirt at the base of his wide neck, and Larionova noticed a sharp, acrid stink from his suit. Dixon had evidently been out on the surface for long hours.

He pulled a hip flask from an environment suit pocket. “You want a drink?” he asked. “Scotch?”

“Sure.”

Dixon poured a measure for Larionova into the flask’s cap, and took a draught himself from the flask’s small mouth.

Larionova drank; the liquor burned her mouth and throat, but it immediately took an edge off her tiredness. “It’s good. But it needs ice.”

He smiled. “Ice we got. Actually, we have tried it; Mercury ice is good, as clean as you like. We’re not going to die of thirst out here, Irina.”

“Tell me what you’ve found, Frank.”

Dixon sat on the edge of the desk, his fat haunches bulging inside the leggings of his environment suit. “Trouble, Irina. We’ve found trouble.”

“I know that much.”

“I think we’re going to have to get off the planet. The System authoritiesand the scientists and conservation groupsare going to climb all over us, if we try to mine here. I wanted to tell you about it, before”

Larionova struggled to contain her irritation and tiredness. “That’s not a problem for Thoth,” she said. “Therefore it’s not a problem for me. We can tell Superet to bring in a water-ice asteroid from the Belt, for our supplies. You know that. Come on, Frank. Tell me why you’re wasting my time down here.”

Dixon took another long pull on his flask, and eyed her.

“There’s life here, Irina,” he said. “Life, inside this frozen ocean. Drink up; I’ll show you.”

The sample was in a case on the surface, beside a data desk. The thing in the case looked like a strip of multicolored meat: perhaps three feet long, crushed and obviously dead; shards of some transparent shell material were embedded in flesh that sparkled with ice crystals.

“We found this inside a two-thousand-yard-deep core,” Dixon said.

Larionova tried to imagine how this would have looked, intact and mobile. “This means nothing to me, Frank. I’m no biologist.”

He grunted, self-deprecating. “Nor me. Nor any of us. Who expected to find life, on Mercury?” Dixon tapped at the data desk with gloved fingers. “We used our desks’ medico-diagnostic facilities to come up with this reconstruction,” he said. “We call it a mercuric, Irina.”

A Virtual projected into space a foot above the desk’s surface; the image rotated, sleek and menacing.

The body was a thin cone, tapering to a tail from a wide, flat head. Three parabolic cupseyes?were embedded in the smooth “face,” symmetrically placed around a lipless mouth… No, not eyes, Larionova corrected herself. Maybe some kind of sonar sensor? That would explain the parabolic profile.

Mandibles, like pincers, protruded from the mouth. From the tail, three fins were splayed out around what looked like an anus. A transparent carapace surrounded the main body, like a cylindrical cloak; inside the carapace, rows of small, hairlike cilia lined the body, supple and vibratile.

There were regular markings, faintly visible, in the surface of the carapace.

“Is this accurate?”

“Who knows? It’s the best we can do. When we have your clearance, we can transmit our data to Earth, and let the experts get at it.”

“Lethe, Frank,” Larionova said. “This looks like a fish. It looks like it could swim. The streamlining, the tail”

Dixon scratched the short hairs at the back of his neck and said nothing.

“But we’re on Mercury, damn it, not in Hawaii,” Larionova said.

Dixon pointed down, past the dusty floor. “Irina. It’s not all frozen. There are cavities down there, inside the Chao ice cap. According to our sonar probes”

“Cavities?”

“Water. At the base of the crater, under a couple of miles of ice. Kept liquid by thermal vents, in crust-collapse scarps and ridges. Plenty of room for swimming… we speculate that our friend here swims on his back” he tapped the desk surface, and the image swiveled “and the water passes down, between his body and this carapace, and he uses all those tiny hairs to filter out particles of food. The trunk seems to be lined with little mouths. See?” He flicked the image to another representation; the skin became transparent, and Larionova could see blocky reconstructions of internal organs. Dixon said, “There’s no true stomach, but there is what looks like a continuous digestive tube passing down the axis of the body, to the anus at the tail.”

Larionova noticed a threadlike structure wrapped around some of the organs, as well as around the axial digestive tract.

“Look,” Dixon said, pointing to one area. “Look at the surface structure of these lengths of tubing, here near the digestive tract.”

Larionova looked. The tubes, clustering around the digestive axis, had complex, rippled surfaces. “So?”

“You don’t get it, do you? It’s convolutedlike the surface of a brain. Irina, we think that stuff must be some equivalent of nervous tissue.”

Larionova frowned. Damn it, I wish I knew more biology. “What about this thread material, wrapped around the organs?”

Dixon sighed. “We don’t know, Irina. It doesn’t seem to fit with the rest of the structure, does it?” He pointed. “Follow the threads back. There’s a broader main body, just here. We think maybe this is some kind of parasite, which has infested the main organism. Like a tapeworm. It’s as if the threads are extended, vestigial limbs…”

Leaning closer, Larionova saw that tendrils from the wormthing had even infiltrated the brain-tubes. She shuddered; if this was a parasite, it was a particularly vile infestation. Maybe the parasite even modified the mercuric’s behavior, she wondered.

Dixon restored the solid-aspect Virtual.

Uneasily, Larionova pointed to the markings on the carapace. They were small triangles, clustered into elaborate patterns. “And what’s this stuff?”

Dixon hesitated. “I was afraid you might ask that.”

“Well?”

“…We think the markings are artificial, Irina. A deliberate tattoo, carved into the carapace, probably with the mandibles. Writing, maybe: those look like symbolic markings, with information content.”

“Lethe,” she said.

“I know. This fish was smart,” Dixon said.

The people, victorious, clustered around the warmth of their new Chimney. Recovering from their journey and from their battle-wounds, they cruised easily over the gardens of cilia-plants, and browsed on floating fragments of food.

It had been a great triumph. The Heads were dead, or driven off into the labyrinth of tunnels through the Ice. Strong-Flukes had even found the Heads’ principal nest here, under the silty floor of the cavern. With sharp stabs of her mandibles, Strong-Flukes had destroyed a dozen or more Head young.

Cilia-of-Gold took herself off, away from the Chimney. She prowled the edge of the Ice cavern, feeding fitfully.

She was a hero. But she couldn’t bear the attention of others: their praise, the warmth of their bodies. All she seemed to desire now was the uncomplicated, silent coolness of Ice.

She brooded on the infestation that was spreading through her.

Seekers were a mystery. Nobody knew why Seekers compelled their hosts to isolate themselves, to bury themselves in the Ice. What was the point? When the hosts were destroyed, so were the Seekers.

Perhaps it wasn’t the Ice itself the Seekers desired, she wondered. Perhaps they sought, in their blind way, something beyond the Ice…

But there was nothing above the Ice. The caverns were hollows in an infinite, eternal Universe of Ice. Cilia-of-Gold, with a shudder, imagined herself burrowing, chewing her way into the endless Ice, upwards without limit… Was that, finally, how her life would end?

She hated the Seeker within her. She hated her body, for betraying her in this way; and she hated herself.

“Cilia-of-Gold.”

She turned, startled, and closed her carapace around herself reflexively.

It was Strong-Flukes and Ice-Born, together. Seeing their warm, familiar bodies, here in this desolate corner of the cavern, Cilia-of-Gold’s loneliness welled up inside her, like a Chimney of emotion.

But she swam away from her Three-mates, backwards, her carapace scraping on the cavern’s Ice wall.

Ice-Born came towards her, hesitantly. “We’re concerned about you.”

“Then don’t be,” she snapped. “Go back to the Chimney, and leave me here.”

“No,” Strong-Flukes said quietly.

Cilia-of-Gold felt desperate, angry, confined. “You know what’s wrong with me, Strong-Flukes. I have a Seeker. It’s going to kill me. And there’s nothing any of us can do about it.”

Their bodies pressed close around her now; she longed to open up her carapace to them and bury herself in their warmth.

“We know we’re going to lose you, Cilia-of-Gold,” Ice-Born said. It sounded as if she could barely speak. Ice-Born had always been the softest, the most loving, of the Three, Cilia-of-Gold thought, the warm heart of their relationship. “And”

“Yes?”

Strong-Flukes opened her carapace wide. “We want to be Three again,” she said.

Already, Cilia-of-Gold saw with a surge of love and excitement, Strong-Flukes’s ovipositor was distended: swollen with one of the three isogametes which would fuse to form a new child, their fourth…

A child Cilia-of-Gold could never see growing to consciousness.

“No!” Her cilia pulsed with the single, agonized word.

Suddenly the warmth of her Three-mates was confining, claustrophobic. She had to get away from this prison of flesh; her mind was filled with visions of the coolness and purity of Ice: of clean, high Ice.

“Cilia-of-Gold. Wait. Please”

She flung herself away, along the wall. She came to a tunnel mouth, and she plunged into it, relishing the tunnel’s cold, stagnant water.

“Cilia-of-Gold! Cilia-of-Gold!”

She hurled her body through the web of tunnels, carelessly colliding with walls of Ice so hard that she could feel her carapace splinter. On and on she swam, until the voices of her Three-mates were lost forever.

We’ve dug out a large part of the artifact, Irina, Dolores Wu reported. It’s a mass of what looks like hull material.

“Did you get a sample?”

No. We don’t have anything that could cut through material so dense… Irina, we’re looking at something beyond our understanding.

Larionova sighed. “Just tell me, Dolores,” she told Wu’s data-desk image.

Irina, we think we’re dealing with the Pauli Principle.

Pauli’s Exclusion Principle stated that no two fermionselectrons or quarkscould exist in the same quantum state. Only a certain number of electrons, for example, could share a given energy level in an atom. Adding more electrons caused complex shells of charge to build up around the atom’s nucleus. It was the electron shellsthis consequence of Paulithat gave the atom its chemical properties.

But the Pauli Principle didn’t apply to photons; it was possible for many photons to share the same quantum state. That was the essence of the laser: billions of photons, coherent, sharing the same quantum properties.

Irina, Wu said slowly, what would happen if you could turn off the Exclusion Principle, for a piece of fermionic matter?

“You can’t,” Larionova said immediately.

Of course not. Try to imagine anyway.

Larionova frowned. What if one could lase mass? “The atomic electron shells would implode, of course.”

Yes.

“All electrons would fall into their ground state. Chemistry would be impossible.”

Yes. But you may not care…

“Molecules would collapse. Atoms would fall into each other, releasing immense quantities of binding energy.”

You’d end up with a super dense substance, wouldn’t you? Completely non-reactive, chemically. And almost unbreachable, given the huge energies required to detach non-Pauli atoms.

Ideal hull material, Irina…

“But it’s all impossible,” Larionova said weakly. “You can’t violate Pauli.”

Of course you can’t, Dolores Wu replied.

Inside an opaqued bubble-shelter, Larionova, Dixon and Scholes sat on fold-out chairs, cradling coffees.

“If your mercuric was so smart,” Larionova said to Dixon, “how come he got himself stuck in the ice?”

Dixon shrugged. “In fact it goes deeper than that. It looked to us as if the mercuric burrowed his way up into the ice, deliberately. What kind of evolutionary advantage could there be in behavior like that? The mercuric was certain to be killed.”

“Yes,” Larionova said. She massaged her temples, thinking about the mercuric’s infection. “But maybe that thread-parasite had something to do with it. I mean, some parasites change the way their hosts behave.”

Scholes tapped at a data desk; text and images, reflected from the desk, flickered over his face. “That’s true. There are parasites which transfer themselves from one host to anotherby forcing a primary host to get itself eaten by the second.”

Dixon’s wide face crumpled. “Lethe. That’s disgusting.”

“The lancet fluke,” Scholes read slowly, “is a parasite of some species of ant. The fluke can make its host climb to the top of a grass stem and then lock onto the stem with its mandiblesand wait until it’s swallowed by a grazing sheep. Then the fluke can go on to infest the sheep in turn.”

“Okay,” Dixon said. “But why would a parasite force its mercuric host to burrow up into the ice of a frozen ocean? When the host dies, the parasite dies, too. It doesn’t make sense.”

“There’s a lot about this that doesn’t make sense,” Larionova said. “Like, the whole question of the existence of life in the cavities in the first place. There’s no light down there. How do the mercurics survive, under two miles of ice?”

Scholes folded one leg on top of the other and scratched his ankle. “I’ve been going through the data desks.” He grimaced, self-deprecating. “A crash course in exotic biology. You want my theory?”

“Go ahead.”

“The thermal ventswhich cause the cavities in the first place. The vents are the key. I think the bottom of the Chao ice-cap is like the mid-Atlantic ridge, back on Earth.

“The deep sea, a mile down, is a desert; by the time any particle of food has drifted down from the richer waters above it’s passed through so many guts that its energy content is exhausted.

“But along the Ridge, where tectonic plates are colliding, you have hydrothermal ventsjust as at the bottom of Chao. And the heat from the Atlantic vents supports life: in little colonies, strung out along the mid-Atlantic Ridge. The vents form superheated fountains, smoking with deep-crust minerals which life can exploit: sulphides of copper, zinc, lead and iron, for instance. And there are very steep temperature differences, and so there are high energy gradientsanother prerequisite for life.”

“Hmm.” Larionova closed her eyes and tried to picture it. Pockets of warm water, deep in the ice of Mercury; luxuriant mats of life surrounding mineral-rich hydrothermal vents, browsed by Dixon’s mercuric animals… was it possible?

Dixon asked, “How long do the vents persist?”

“On Earth, in the Ridge, a couple of decades. Here we don’t know.”

“What happens when a vent dies?” Larionova asked. “That’s the end of your pocket world, isn’t it? The ice chamber would simply freeze up.”

“Maybe,” Scholes said. “But the vents would occur in rows, along the scarps. Maybe there are corridors of liquid water, within the ice, along which mercurics could migrate.”

Larionova thought about that for a while.

“I don’t believe it,” she said.

“Why not?”

“I don’t see how it’s possible for life to have evolved here in the first place.” In the primeval oceans of Earth, there had been complex chemicals, and electrical storms, and…

“Oh, I don’t think that’s a problem,” Scholes said.

She looked at him sharply. Maddeningly, he was grinning again. “Well?” she snapped.

“Look,” Scholes said with grating patience, “we’ve two anomalies on Mercury: the life-forms here at the South Pole, and Dolores Wu’s artifact under Caloris. The simplest assumption is that the two anomalies are connected. Let’s put the pieces together,” he said. “Let’s construct a hypothesis…”

Her mandibles ached as she crushed the gritty Ice, carving out her tunnel upwards. The rough walls of the tunnel scraped against her carapace, and she pushed Ice rubble down between her body and her carapace, sacrificing fragile cilia designed to extract soft food particles from warm streams.

The higher she climbed, the harder the Ice became. The Ice was now so cold she was beyond cold; she couldn’t even feel the Ice fragments that scraped along her belly and flukes. And, she suspected, the tunnel behind her was no longer open but had refrozen, sealing her here, in this shifting cage, forever. The world she had leftof caverns, and Chimneys, and children, and her Three-mateswere remote bubbles of warmth, a distant dream. The only reality was the hard Ice in her mandibles, and the Seeker heavy and questing inside her.

She could feel her strength seeping out with the last of her warmth into the Ice’s infinite extent. And yet still the Seeker wasn’t satisfied; still she had to climb, on and up, into the endless darkness of the Ice.

…But nowimpossiblythere was something above her, breaking through the Ice…

She cowered inside her Ice-prison.

Kevan Scholes said, “Five billion years agowhen the Solar System was very young, and the crusts of Earth and other inner planets were still subject to bombardment from stray planetesimalsa ship came here. An interstellar craft, maybe with FTL technology.”

“Why? Where from?” Larionova asked.

“I don’t know. How could I know that? But the ship must have been massivewith the bulk of a planetesimal, or more. Certainly highly advanced, with a hull composed of Dolores’ super dense Pauli construction material.”

“Hmm. Go on.”

“Then the ship hit trouble.”

“What kind of trouble?”

“I don’t know. Come on, Dr. Larionova. Maybe it got hit by a planetesimal itself. Anyway, the ship crashed here, on Mercury”

“Right.” Dixon nodded, gazing at Scholes hungrily; the American reminded Larionova of a child enthralled by a story. “It was a disastrous impact. It caused the Caloris feature…”

“Oh, be serious,” Larionova said.

Dixon looked at her. “Caloris was a pretty unique impact, Irina. Extraordinarily violent, even by the standards of the System’s early bombardment phase… Caloris Basin is eight hundred miles across; on Earth, its walls would stretch from New York to Chicago.”

“So how did anything survive?”

Scholes shrugged. “Maybe the starfarers had some kind of inertial shielding. How can we know? Anyway the ship was wrecked; and the density of the smashed-up hull material caused it to sink into the bulk of the planet, through the Caloris puncture.

“The crew were stranded. So they sought a place to survive. Here, on Mercury.”

“I get it,” Dixon said. “The only viable environment, long term, was the Chao Meng-Fu ice cap.”

Scholes spread his hands. “Maybe the starfarers had to engineer descendants, quite unlike the original crew, to survive in such conditions. And perhaps they had to do a little planetary engineering too; they may have had to initiate some of the hydrothermal vents which created the enclosed liquid-water world down there. And so”

“Yes?”

“And so the creature we’ve dug out of the ice is a degenerate descendant of those ancient star travelers, still swimming around the Chao Sea.”

Scholes fell silent, his eyes on Larionova.

Larionova stared into her coffee. “A ‘degenerate descendant.’ After five billion years? Look, Scholes, on Earth it’s only three and a half billion years since the first prokaryotic cells. And on Earth, whole phylagroups of specieshave emerged or declined over periods less than a tenth of the time since the Caloris Basin event. Over time intervals like that, the morphology of species flows like hot plastic. So how is it possible for these mercurics to have persisted?”

Scholes looked uncertain. “Maybe they’ve suffered massive evolutionary changes,” he said. “But we’re just not recognizing them. For example, maybe the worm parasite is the malevolent descendant of some harmless creature the starfarers brought with them.”

Dixon scratched his neck, where the suit-collar ring of dirt was prominent. “Anyway, we’ve still got the puzzle of the mercuric’s burrowing into the ice.”

“Hmm.” Scholes sipped his cooling coffee. “I’ve got a theory about that, too.”

“I thought you might,” Larionova said sourly.

Scholes said, “I wonder if the impulse to climb up to the surface is some kind of residual yearning for the stars.”

“What?”

Scholes looked embarrassed, but he pressed on: “A racial memory buried deep, prompting the mercurics to seek their lost home world… why not?”

Larionova snorted. “You’re a romantic, Kevan Scholes.”

A telltale flashed on the surface of the data desk. Dixon leaned over, tapped the telltale and took the call.

He looked up at Larionova, his moonlike face animated. “Irina. They’ve found another mercuric,” he said.

“Is it intact?”

“More than that.” Dixon stood and reached for his helmet. “This one isn’t dead yet…”

The mercuric lay on Chao’s dust-coated ice. Humans stood around it, suited, their face plates anonymously blank.

The mercuric, dying, was a cone of bruised-purple meat a yard long. Shards of shattered transparent carapace had been crushed into its crystallizing flesh. Some of the cilia, within the carapace, stretched and twitched. The cilia looked differently colored to Dixon’s reconstruction, as far as Larionova could remember: these were yellowish threads, almost golden.

Dixon spoke quickly to his team, then joined Larionova and Scholes. “We couldn’t have saved it. It was in distress as soon as our core broke through into its tunnel. I guess it couldn’t take the pressure and temperature differentials. Its internal organs seem to be massively disrupted…”

“Just think.” Kevan Scholes stood beside Dixon, his hands clasped behind his back. “There must be millions of these animals in the ice under our feet, embedded in their pointless little chambers. Surely none of them could dig more than a hundred yards or so up from the liquid layer.”

Larionova switched their voices out of her consciousness. She knelt down, on the ice; under her knees she could feel the criss-cross heating elements in her suit’s fabric.

She peered into the dulling sonar-eyes of the mercuric. The creature’s mandiblesprominent and sharpopened and closed, in vacuum silence.

She felt an impulse to reach out her gloved hand to the battered flank of the creature: to touch this animal, this person, whose species had, perhaps, traveled across light yearsand five billion yearsto reach her…

But still, she had the nagging feeling that something was wrong with Scholes’ neat hypothesis. The mercuric’s physical design seemed crude. Could this really have been a starfaring species? The builders of the ship in Caloris must have had some form of major tool-wielding capability. And Dixon’s earlier study had shown that the creature had no trace of any limbs, even vestigially…

Vestigial limbs, she remembered. Lethe.

Abruptly her perception of this animaland its host parasitebegan to shift; she could feel a paradigm dissolving inside her, melting like a Mercury snowflake in the Sun.

“Dr. Larionova? Are you all right?”

Larionova looked up at Scholes. “Kevan, I called you a romantic. But I think you were almost correct, after all. But not quite. Remember we’ve suggested that the parasitethe infestationchanges the mercuric’s behavior, causing it to make its climb.”

“What are you saying?”

Suddenly, Larionova saw it all. “I don’t believe this mercuric is descended from the starfarersthe builders of the ship in Caloris. I think the rise of the mercurics’ intelligence was a later development; the mercurics grew to consciousness here, on Mercury. I do think the mercurics are descended from something that came to Mercury on that ship, though. A pet, or a food animalLethe, even some equivalent of a stomach bacteria. Five billion years is time enough for anything. And, given the competition for space near the short-lived vents, there’s plenty of encouragement for the development of intelligence, down inside this frozen sea.”

“And the starfarers themselves?” Scholes asked. “What became of them? Did they die?”

“No,” she said. “No, I don’t think so. But they, too, suffered huge evolutionary changes. I think they did devolve, Scholes; in fact, I think they lost their awareness.

“But one thing persisted within them, across all this desert of time. And that was the starfarers’ vestigial will to returnto the surface, one day, and at last to the stars…”

It was a will which had survived even the loss of consciousness itself, somewhere in the long, stranded aeons: a relic of awareness long since transmuted to a deeper biochemical urgea will to return home, still embedded within a once-intelligent species reduced by time to a mere parasitic infection.

But it was a home which, surely, could no longer exist.

The mercuric’s golden cilia twitched once more, in a great wave of motion which shuddered down its ice-flecked body.

Then it was still.

Larionova stood up; her knees and calves were stiff and cold, despite the suit’s heater. “Come on,” she said to Scholes and Dixon. “You’d better get your team off the ice as soon as possible; I’ll bet the universities have their first exploratory teams down here half a day after we pass Earth the news.”

Dixon nodded. “And Thoth?”

“Thoth? I’ll call Superet. I guess I’ve an asteroid to order…”

And then she thought, at last I can sleep. Sleep and get back to work.

With Scholes and Dixon, she trudged across the dust-strewn ice to the bubble-shelters.

She could feel the Ice under her belly… but above her there was no Ice, no water even, an infinite nothing into which the desperate pulses of her blinded eyes disappeared without echo.

Astonishinglyimpossiblyshe was, after all, above the Ice. How could this be? Was she in some immense upper cavern, its Ice roof too remote to see? Was this the nature of the Universe, a hierarchy of caverns within caverns?

She knew she would never understand. But it didn’t seem to matter. And, as her awareness faded, she felt the Seeker inside her subside to peace.

A final warmth spread out within her. Consciousness splintered like melting ice, flowing away through the closing tunnels of her memory.

“At last,” Eve told me, “the Thoth Sun probe hardware was ready. Now, all that was needed was the software…”

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